Method of producing aluminum substrate for planographic printing plate and method of recycling planographic printing plate

ABSTRACT

A method of producing an aluminum substrate for a planographic printing plate is provided in which a recycled material including a used planographic printing plate having a planographic printing plate support obtained by treating an aluminum substrate is prepared, a recycled bare metal is obtained from the recycled material, and a new aluminum bare metal and a trace-metal master alloy of necessary amounts are mixed into the recycled bare metal to produce a new aluminum substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 from Japanese PatentApplication No. 2009-222874 filed on Sep. 28, 2009, and No. 2009-227792filed on Sep. 30, 2009, the disclosures of which are incorporated byreference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of producing an aluminumsubstrate for a planographic printing plate, and more particularly, to amethod of producing an aluminum substrate for a planographic printingplate, in which a used planographic printing plate is efficientlyrecycling, and a method of recycling a planographic printing plate usingthe production method.

2. Description of the Related Art

Planographic printing plates are produced by forming an image recordinglayer (for example, a photosensitive layer) on an aluminum planographicprinting plate support. Since such an aluminum substrate needs to besubjected to a uniform and dense roughening treatment, that is, asurface treatment such as an electrochemical roughening treatment, a rawmaterial with high purity and a strictly-adjusted trace metal contentshould be used as the aluminum material of the aluminum substrate.

On the other hand, energy of 140.9 MJ is theoretically required forproducing 1 kg of new metal aluminum and the amount of CO₂ generated atthe time is 9.22 kg/kg. Accordingly, when it is intended to produce aplanographic printing plate while suppressing the generation of CO₂ asmuch as possible, it can be thought that end materials such as cutpieces generated in a used planographic printing plate having been usedin printing or during producing a planographic printing plate arerecycled as a recycled aluminum material. However, since the purity orthe alloy composition of the recycled aluminum material does not reachthe level required as the raw material of the planographic printingplate support, it is difficult to use the aluminum material recycledfrom a recovered planographic printing plate as a planographic printingplate support. The recycled aluminum material is generally used inapplications in which the purity of the contained metal need not bestrictly managed, for example, as a raw material of a window chassis, avehicle engine, or a vehicle wheel, but is not provided for theplanographic printing plate.

However, the production energy for producing 1 kg of a recycled baremetal containing a used planographic printing plate or end materialssuch as cut pieces of a planographic printing plate is only about 4% of140.9 MJ. Accordingly, if such materials can be recycled for aplanographic printing plate, it is possible to effectively reduce thegeneration of CO₂. For this purpose, it is important to construct arecycling method of guaranteeing the quality as an aluminum substratefor the planographic printing plate and then reducing the energy.

Recently, recycling used planographic printing plates or the endmaterials as a recycled material has been studied. For example, a methodof recycling a used planographic printing plate as a support by removingimpurities from the used planographic printing plate, adding newaluminum bare metal and master alloy (aluminum alloy containing severaltens of % of the desired metal) thereto, directly introducing theresultant into a pre-rolling melting furnace to produce a melt,performing a filtering process thereon, and rolling the resultant isdisclosed (for example, see Japanese Patent No. 3420817). It issuggested that the production cost of the aluminum substrate for theplanographic printing plate is lowered by recycling used aluminummaterial for the aluminum substrate for the planographic printing plateformed of low-purity aluminum (for example, see Japanese PatentApplication Laid-Open (JP-A) No. 2002-331767).

However, in the case of JP-A No. 2002-331767, when the low-purityaluminum is used as a base material of the substrate, various othermeans are necessary for accomplishing the adhesive strength to an imagerecording layer formed on the surface of the support or the hydrophilicproperty sufficient for serving as a non-image area.

In the method described in Japanese Patent No. 3420817, since a method(hereinafter, referred to as “direct introduction method”) of directlyintroducing the used planographic printing plate into a pre-rollingmelting furnace for forming a support is used, it is difficult to avoidthe great influence of the composition of the used aluminum to beintroduced on the alloy composition of the rolled aluminum plate.However, as described above, when the process of roughening theplanographic printing plate, for example, the roughening treatment usingan electrolysis method, is performed, the alloy composition of thealuminum plate has a critical influence on the roughened shape.Accordingly, when it is intended to obtain an aluminum substrate with ahigher purity necessary for the roughening treatment using anelectrolysis method, the amount of used planographic printing plate tobe introduced is limited in view of quality and it is necessary to use alarge amount of aluminum with a high purity. Therefore, the recyclingefficiency is poor and it is not preferable in view of a reduction incarbon dioxide. It is necessary to measure the impurity composition inthe course of performing the introduction into the melting furnace andperforming the rolling process and the melting or the compositionadjustment requires time, which causes deterioration in yield.

SUMMARY OF THE INVENTION

The invention is made in view of the above-mentioned situation. Thepresent invention provides a method of producing an aluminum substratefor a planographic printing plate, which can produce an aluminumsubstrate for a planographic printing plate satisfying the quality ofaluminum purity or trace-metal content with a high yield even when aused planographic printing plate is reused at the time of producing analuminum substrate for a planographic printing plate and which canreduce the accompanying amount of aluminum oxide generated and greatlyreduce the generation of CO₂, a cause of global warming.

The present invention also provides a method of recycling a planographicprinting plate with high efficiency which can greatly reduce thegeneration of CO₂ in processes by using the above-mentioned method ofproducing an aluminum substrate for a planographic printing plate.

As a result of vigorous study, the inventors have been discovered thatthe above-mentioned object could be accomplished by using a usedplanographic printing plate including an aluminum substrate having beensubjected to specific surface treatment, whereby the invention was made.

That is, according to the invention, there is provided a method ofproducing an aluminum substrate for a planographic printing plate, themethod sequentially including:

preparing a recycled material including a used planographic printingplate having a planographic printing plate support obtained by treatingan aluminum substrate;

producing a recycled bare metal by introducing the obtained recycledmaterial into a melting furnace, melting the recycled material at atemperature of from 680° C. to 900° C. to obtain a recycled materialmelt, and shaping the recycled material melt into a predetermined shapewith a predetermined weight;

analyzing the aluminum purity and a trace metal content of the obtainedrecycled bare metal;

comparing analysis values of the aluminum purity and the trace metalcontent of the obtained recycled bare metal with a desired aluminumpurity and a desired trace metal content predetermined for aplanographic printing plate support in order to calculate differencestherebetween, and determining a mixture ratio of a new aluminum baremetal and a trace-metal master alloy with a determined purity withrespect to the recycled bare metal on the basis of the calculateddifferences;

producing a pre-rolling melt by introducing the recycled bare metal, thenew aluminum bare metal, and the trace-metal master alloy into apre-rolling melting furnace at amounts corresponding to the determinedmixture ratio, and heating and melting; and

producing a strip-shaped aluminum substrate by rolling the obtainedpre-rolling melt.

In the method of producing an aluminum substrate for a planographicprinting plate according to a first embodiment of the invention, theplanographic printing plate support is obtained by sequentiallyperforming a roughening treatment, an anodization treatment, and ahydrophilizing treatment using an aqueous solution containing polyvinylphosphonic acid on the aluminum substrate.

Furthermore, as a result of vigorous study, the inventors have beendiscovered that the above-mentioned object could be accomplished byusing a used planographic printing plate including an aluminum substrateformed of aluminum alloy containing a specific amount of Cu, whereby theinvention was made.

That is, in the method of producing an aluminum substrate for aplanographic printing plate according to a second embodiment of theinvention, the planographic printing plate support is obtained bysequentially performing a roughening treatment and an anodizationtreatment using an electrolytic solution containing phosphoric acid onthe aluminum substrate.

The recycled material, which is used in the production method accordingto the invention, of the aluminum substrate including a usedplanographic printing plate is not particularly limited to the usedplanographic printing plate, but may include cut pieces of an aluminumsubstrate or cut pieces of a planographic printing plate, which aregenerated in the course of producing the planographic printing plate.

According to a first embodiment of the invention, there is provided amethod of recycling a planographic printing plate, the methodsequentially including:

producing a planographic printing plate support obtained by treating analuminum substrate for the planographic printing plate;

producing a planographic printing plate precursor by forming an imagerecording layer on the treated surface of the planographic printingplate support;

processing the obtained planographic printing plate precursor to obtaina planographic printing plate and performing a desired printing on theobtained planographic printing plate;

recovering the used planographic printing plate generated afterprinting; and

recycling the recovered planographic printing plate by providing therecovered planographic printing plate as the recycled material of analuminum substrate in the method of producing an aluminum substrate fora planographic printing plate.

In the method of producing an aluminum substrate for a planographicprinting plate according to a first embodiment of the invention, theplanographic printing plate support is obtained by sequentiallyperforming a roughening treatment, an anodization treatment, and ahydrophilizing treatment using an aqueous solution including polyvinylphosphonic acid on at least one surface of an aluminum substrate.

Further, in the method of producing an aluminum substrate for aplanographic printing plate according to a second embodiment of theinvention, the planographic printing plate support is obtained bysequentially performing a roughening treatment and an anodizationtreatment using an electrolytic solution including phosphoric acid on atleast one surface of an aluminum substrate.

Here, the aluminum substrate for the planographic printing plate may bethe recycled aluminum substrate for the planographic printing plateobtained by the above-mentioned method of producing an aluminumsubstrate for a planographic printing plate.

Although the function of the method according to the first embodiment ofthe invention is not clear, it is thought that the support used in theinvention made to be hydrophilic using the polyvinyl phosphonic acidreduces the amount of aluminum oxide, which is an oxide materialgenerated by the contact of aluminum with air at the time of meltingaluminum during producing the recycled bare metal, in comparison with analuminum substrate not having been subjected to the above-mentionedtreatment, whereby the loss of the aluminum material is small and thesupport can be recycled with high yield.

Although the function in the method according to the second embodimentof the invention is not clear, it is assumed as follows.

In the aluminum substrate for the planographic printing plate havingbeen subjected to the anodization treatment using an electrolyticsolution containing phosphoric acid, the pore diameter of the anodizedoxide film formed on the surface of the support is greater than that ofthe anodized oxide film formed using an electrolytic solution containinggenerally-used sulfuric acid. Since such a support is rapidly melted dueto the large pore diameter when preparing the melt by heating duringproduction of the recycled bare metal, the duration of time that therecycled material contacts air under a high-temperature condition isshortened in comparison with a support including an anodized oxide filmhaving plural pores with a small pore diameter. Accordingly, since theamount of undesired aluminum oxide to be generated is reduced, it isconceived that the loss of the aluminum material is small and thesupport can be recycled with high yield. The ratio of phosphoric acid inthe acid components of the electrolytic solution used in the inventionis not particularly limited, but is preferably 5% by mass or higher inview of efficiency, and the acid components in the electrolytic solutionmay include only phosphoric acid.

The invention includes determining the mixture ratio by analyzing thealuminum purity and the trace-metal content of the obtained recycledbare metal or the recycled melt, comparing the analyzed values with adesired aluminum purity and the desired trace-metal content of aplanographic printing plate in order to calculate differencestherebetween, and determining the mixture ratio of a new aluminum baremetal and trace-metal master alloy on the basis of the differences, andthus the ratio for mixing the maximum amount of recycled bare metal isdetermined, whereby recycling with high yield is accomplished withreduced loss of raw material.

Here, the “desired aluminum purity and the desired trace-metal contentof a planographic printing plate support” means the “aluminum purity andthe trace-metal content” required depending on the types of theplanographic printing plates to be produced, and the optimal values aredetermined in advance depending on the required performance of therespective planographic printing plates.

Therefore, according to the invention, since the ratio for mixing themaximum amount of recycled bare metal can be determined with highprecision on the basis of the set values, it is possible to greatlyreduce the amount of the new aluminum bare metal used, which consumesgreat energy in the production thereof, and it is thus possible toeffectively reduce the amount of carbon dioxide in producing an aluminumsubstrate for a planographic printing plate.

Accordingly, even when a used planographic printing plate is reused atthe time of producing an aluminum substrate for a planographic printingplate, it is possible to greatly reduce the loss of energy and of yield.

The present invention provides a method of producing an aluminumsubstrate for a planographic printing plate, which can produce analuminum substrate for a planographic printing plate satisfying thequality of aluminum purity or trace-metal content with a high yield evenwhen a used planographic printing plate is reused at the time ofproducing an aluminum substrate for a planographic printing plate andwhich can reduce the accompanying amount of aluminum oxide generated andgreatly reduce the generation of CO₂, a cause of global warming.

The present invention also provides a method of recycling a planographicprinting plate with high efficiency which can greatly reduce thegeneration of CO₂ in the processes by using the above-mentioned methodof producing an aluminum substrate for a planographic printing plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described indetail based on the following figures, wherein:

FIG. 1 is a schematic diagram illustrating a flow of closed-looprecycling in a method of recycling a planographic printing plate;

FIG. 2 is a schematic diagram illustrating an example of a recycled baremetal producing apparatus in which recycled bare metal is produced froma used planographic printing plate;

FIG. 3A is a plan view illustrating a trapezoidally-shaped recycled baremetal obtained by the method according to the invention; and

FIG. 3B is a side view illustrating a trapezoidally-shaped recycled baremetal obtained by the method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinbelow, preferable embodiment of a method of producing an aluminumsubstrate for a planographic printing plate and a method of recycling aplanographic printing plate according to the invention is described indetail.

Method of producing aluminum substrate for planographic printing plate

The method of producing an aluminum substrate for a planographicprinting plate according to a first embodiment of the inventionsequentially includes:

preparing recycled material including a used planographic printing platehaving a planographic printing plate support obtained by sequentiallyperforming a roughening treatment, an anodization treatment, and ahydrophilizing treatment using an aqueous solution containing polyvinylphosphonic acid on the aluminum substrate;

producing a recycled bare metal by introducing the obtained recycledmaterial into a melting furnace, melting the recycled material at atemperature of from 680° C. to 900° C. to obtain a recycled materialmelt, and shaping the recycled material melt into a predetermined shapewith a predetermined weight;

analyzing the aluminum purity and a trace metal content of the obtainedrecycled bare metal;

comparing analysis values of the aluminum purity and the trace metalcontent of the obtained recycled bare metal with a desired aluminumpurity and a desired trace metal content predetermined for aplanographic printing plate support in order to calculate differencestherebetween, and determining a mixture ratio of new aluminum bare metaland a trace-metal master alloy with a determined purity with respect tothe recycled bare metal on the basis of the calculated differences;

producing a pre-rolling melt by introducing the recycled bare metal, thenew aluminum bare metal, and the trace-metal master alloy into apre-rolling melting furnace at amounts corresponding to the determinedmixture ratio, and heating and melting; and

producing a strip-shaped aluminum substrate by rolling the obtainedpre-rolling melt.

The method of producing an aluminum substrate for a planographicprinting plate according to a second embodiment of the inventionsequentially includes:

preparing a recycled material including a used planographic printingplate having a planographic printing plate support obtained bysequentially performing a roughening treatment and an anodizationtreatment using an electrolytic solution including phosphoric acid onthe aluminum substrate;

producing a recycled bare metal by introducing the obtained recycledmaterial into a melting furnace, melting the recycled material at atemperature of from 680° C. to 900° C. to obtain a recycled materialmelt, and shaping the recycled material melt into a predetermined shapewith a predetermined weight;

analyzing the aluminum purity and a trace metal content of the obtainedrecycled bare metal;

comparing analysis values of the aluminum purity and the trace metalcontent of the obtained recycled bare metal with a desired aluminumpurity and a desired trace metal content predetermined for aplanographic printing plate support in order to calculate differencestherebetween, and determining a mixture ratio of a new aluminum baremetal and a trace-metal master alloy with a determined purity withrespect to the recycled bare metal on the basis of the calculateddifferences;

producing a pre-rolling melt by introducing the recycled bare metal, thenew aluminum bare metal, and the trace-metal master alloy into apre-rolling melting furnace at amounts corresponding to the determinedmixture ratio, and heating and melting; and

producing a strip-shaped aluminum substrate by a rolling the obtainedpre-rolling melt.

Hereinbelow, the present invention is described in detail.

Planographic Printing Plate Support

The support used in the production method according to the firstembodiment of the invention is a planographic printing plate supportobtained by sequentially performing a roughening treatment, ananodization treatment, and a hydrophilizing treatment using an aqueoussolution containing polyvinyl phosphonic acid on an aluminum substrate.

The support used in the production method according to the secondembodiment of the invention is a planographic printing plate supportobtained by sequentially performing a roughening treatment and ananodization treatment using an electrolytic solution containingphosphoric acid on an aluminum substrate.

Aluminum Substrate

First, an aluminum substrate is prepared.

As aluminum which is a raw material of the aluminum substrate used inthe invention, a known material such as JIS1050, JIS1100, JIS3003,JIS3103, or JIS3005 material, which are described in the fourth versionof Aluminum Handbook (1990), Japan Light Metal Association) can be used.The aluminum substrate used in the second embodiment of the inventionhas an aluminum (Al) content of 95% by mass to 99.4% by mass and mayfurther contain a trace metal such as copper (Cu), iron (Fe), silicon(Si), magnesium (Mg), manganese (Mn), zinc (Zn), chrome (Cr), ortitanium (Ti).

The Al content in the aluminum alloy as the substrate is preferably inthe range of from 95% by mass to 99.4% by mass. When the Al content inthe aluminum alloy is within the above range, the high recycling rate ofthe aluminum substrate can be accomplished.

The aluminum substrate used in the invention is produced byappropriately performing a rolling treatment or a heating treatment onthe resultant that is molded by a conventional method using theabove-mentioned aluminum as a raw material to make the thickness 0.1 nmto 0.7 mm, and performing a remedial leveling treatment if necessary.

Examples of the method of molding an aluminum substrate include a DCcasting method, a method in which a soaking treatment and/or anannealing treatment is omitted from the DC casting method, and acontinuous casting method.

Roughening Treatment

The aluminum substrate used in the invention is subjected to aroughening treatment. Examples of the roughening method include achemical etching method, an electrochemical roughening method in whichroughening treatment is electrochemically performed in a hydrochloric ornitric electrolytic solution, and a mechanical roughening method using awire brush grain, a ball grain, and a brush grain roughening the surfacewith a nylon brush and an abrasive compound. The roughening methods maybe used singly or in combination of two or more thereof. Among these, itis useful to use the electrochemical roughening method in whichroughening treatment is chemically performed in a hydrochloric or nitricelectrolytic solution. The amount of electricity suitable for the anodeis in the range of from 50 C/dm² to 400 C/dm². More specifically, it ispreferable that the AC and/or DC electrolysis is performed under theconditions of a temperature of from 20° C. to 80° C., a time of 1 secondto 30 minutes, and a current density of from 100 C/dm² to 400 C/dm² inthe electrolytic solution containing hydrochloric acid or nitric acid of0.1% to 50%.

The aluminum substrate having been subjected to the roughening treatmentmay be chemically etched using acid or alkali. Preferable examples of anetching agent include sodium hydroxide, sodium carbonate, sodiumaluminate, sodium metasilicate, sodium phosphate, potassium hydroxide,and lithium hydroxide. The concentration and the temperature arepreferably in the range of from 1% to 50% and in the range of from 20°C. to 100° C., respectively. To remove the contamination (smut)remaining on the etched surface, an acid wash is performed. Examples ofthe acid include nitric acid, sulfuric acid, phosphoric acid, chromicacid, fluoric acid, hydrofluoric acid, and hydrofluoboric acid.

The methods and conditions of the roughening treatment are notparticularly limited, as long as the center line average roughness (Ra)of the treated surface is in the range of from 0.2 μm to 0.55 μm.

Anodization Treatment in First Embodiment

In the first embodiment of the invention, the roughened aluminumsubstrate is subjected to an anodization treatment to form an oxide filmthereon. In the anodization treatment, an aqueous solution of sulfuricacid, phosphoric acid, oxalic acid or boric acid/sodium borate is usedsingly or in combination thereof as a major component of theelectrolytic bath. The conditions of the anodization treatment is notparticularly limited, but the anodization treatment is preferablyperformed by DC or AC electrolysis under the conditions of from 30 g/Lto 500 g/L, a processing solution temperature of from 10° C. to 70° C.,and a current density of from 0.1 A/m² to 40 A/m². The thickness of theanodized oxide film is preferably in the range of from 0.5 μm to 1.5 μmand more preferably in the range of from 0.5 to 1.0 μm.

Anodization Treatment in Second Embodiment

In the second embodiment of the invention, the roughened aluminumsubstrate is subjected to the anodization treatment using anelectrolytic solution containing phosphoric acid to form an oxide filmthereon.

In the second embodiment of the invention, the electrolytic solutioncontaining phosphoric acid is used for anodization treatment. Thecontent of phosphoric acid in the electrolytic solution is notparticularly limited, but, in view of effect, the content of phosphoricacid with respect to the acid component contained in the electrolyticsolution is preferably 5% by mass or higher, more preferably 70% by massor higher, and still more preferably 90% by mass. The acid component mayinclude only phosphoric acid.

The content of phosphoric acid in the electrolytic solution ispreferably in the range of from 10% by mass to 50% by mass, and morepreferably in the range of from 20% by mass to 40% by mass. Theelectrolytic solution is generally an aqueous solution containingphosphoric acid as a major component.

The electrolytic solution used in the second embodiment of the inventionmay contain other acid components used in the anodization treatment,such as sulfuric acid, oxalic acid, or boric acid/sodium borate, as longas the effect of the invention is not deteriorated. The electrolyticsolution generally is an aqueous solution of the above-mentioned acidcomponents, and the acid components including phosphoric acid as a majorcomponent thereof are used singly or in combination.

The electrolytic solution may contain known additives other than theacid components containing phosphoric acid.

In the second embodiment of the invention, the conditions of theanodization treatment using the electrolytic solution containingphosphoric acid are not particularly limited, but the temperature of theprocessing solution is preferably in the range of from 10° C. to 70° C.,more preferably in the range of from 10° C. to 50° C., and still morepreferably in the range of from 25° C. to 45° C. The current densityused in the DC or AC electrolysis is in the range of from 0.1 A/m² to 40A/m², preferably in the range of from 0.2 A/m² to 10 A/m², morepreferably in the range of from 1 A/m² to 7 A/m². The process time canbe appropriately selected depending on the thickness of the anodizedoxide film to be formed, is preferably in the range of from 10 secondsto 10 minutes, and more preferably in the range of from 20 seconds to 3minutes.

The thickness of the anodized oxide film formed in the second embodimentof the invention is preferably in the range of from 0.5 μm to 1.5 μm andmore preferably in the range of from 0.5 μm to 1.0 μm.

When the anodization treatment is performed using the electrolyticsolution containing phosphoric acid, the pore diameter of the anodizedoxide film to be formed increases. The average pore diameter of thepores in the oxide film is preferably in the range of from 200 Å to 900Å, more preferably in the range of from 300 Å to 900 Å, and, still morepreferably in the range of from 400 Å to 900 Å. Since the pore diameterof the anodized oxide film generally formed by the electrolytic solutioncontaining sulfuric acid is around 100 Å, it can be seen that pores witha greater diameter are formed using the electrolytic solution containingphosphoric acid. The average pore density is preferably in the range offrom 100/μm² to 1000/μm², more preferably in the range of from 100/μm²to 500/μm², and still more preferably in the range of from 100/μm² to350/μm².

The average pore diameter and pore density of the pores in the secondembodiment of the invention are average values which are obtained bytaking an image of the surface of the anodized oxide film with anelectron microscope and measuring the pore diameter of the pores and thenumber of pores in the unit area in the electron microscopic image tocalculate the average pore diameter and density, and performing theseprocesses on five positions in the anodized oxide film.

In the anodization method according to the second embodiment of theinvention, the anodized oxide film having pores with an average porediameter of 200 Å or greater and preferably 300 Å or greater is formed.Accordingly, when the planographic printing plate using such a supportis recycled, the used planographic printing plate is rapidly andefficiently melted at the time of producing a melt in the production ofthe recycled bare metal, thereby reducing the amount of undesirablealuminum oxide incidentally produced.

Hydrophilizing Treatment Using Aqueous Solution Containing PolyvinylPhosphonic Acid in First Embodiment

In the first embodiment of the invention, as described above, thesupport which has the anodized oxide film formed thereon and thentreated with the aqueous solution containing polyvinyl phosphonic acidis used.

Examples of the treatment using the aqueous solution containingpolyvinyl phosphonic acid used in the first embodiment of the inventioninclude a treatment method using polyvinyl phosphonic acid described asa hydrophilizing treatment in U.S. Pat. No. 4,153,461. For example, analuminum substrate is treated by immersing it in the below-describedaqueous solution. Other than the immersion, the aqueous solution may beapplied with a brush, a sponge, a spray, a wheel coater, or the like.After the treatment, washing with water and drying may be performed asnecessary.

The polyvinyl phosphonic acid is vinyl polymer having a phosphonategroup and has preferably a number average molecular weight of from10,000 to 25,000. The content of polyvinyl phosphonic acid is preferablyin the range of from 0.1% by mass to 5.0% by mass in the aqueoussolution. The processing temperature is preferably in the range of from20° C. to 90° C. and the processing time is preferably in the range offrom 10 seconds to 30 seconds. The aqueous solution may be an aqueoussolution containing a volatile solvent such as ethyl alcohol,tetrahydrofuran, acetone, or methyl glycol acetate.

The amount of polyvinyl phosphate acid attached to the surface of thesupport having been subjected to the surface treatment using polyvinylphosphonic acid is preferably in the range of from 8 mg/m² to 20 mg/m²in terms of the content of the phosphorous element. When the attachedamount is small, it is not sufficient to suppress the production ofaluminum oxide. The attached amount can be measured by the measurementof element content using fluorescent X ray.

Hydrophilizing Treatment in Second Embodiment

In the second embodiment of the invention, the anodized oxide film isformed as described above and then a hydrophilizing treatment may beperformed on the surface thereof. As the hydrophilizing treatment, amethod using an alkali metal silicate (for example, aqueous solution ofsodium silicate) such as those described in U.S. Pat. Nos. 2,714,066,3,181,461, 3,280,734, and 3,902,734 can be preferably used. In thismethod, the support is immersed in the aqueous solution of sodiumsilicate or is electrolyzed in the aqueous solution of sodium silicate.Preferable examples of the methods also include processing methods usingpotassium fluorozirconate as disclosed in Japanese Examined PatentApplication Publication (JP-B) No. 36-22063, and using polyvinylphosphonic acid as disclosed in U.S. Pat. Nos. 3,276,868, 4,153,461, and4,689,272. Among these, the hydrophilizing treatment is preferablyperformed using aqueous solutions of sodium silicate and polyvinylphosphonic acid.

The aluminum substrate produced in the first embodiment or the secondembodiment preferably has a surface roughness (Ra) of from 0.2 μm to0.55 μm. When the surface roughness (Ra) is 0.2 μm or more, theincompleteness in graining of the aluminum substrate can be moreeffectively suppressed and printing durability can be improved. When thesurface roughness (Ra) is 0.55 μm or less, deterioration inreproducibility of small points and fine lines due to the difficulty inphoto-polymerization at a deep part of the grained surface can be moreeffectively suppressed. The surface roughness (Ra) (roughness of thegrained surface) is more preferably in the range of from 0.25 μm to 0.5μm, and still more preferably in the range of from 0.3 μm to 0.45 μm.

In general, an image recording layer formed of a photosensitivecomposition depending on purposes is formed on the surface of thesupport, thereby obtaining a planographic printing plate precursor.

Preferable examples of the photosensitive composition used in theinvention include a thermal positive photosensitive compositioncontaining a photothermal material and an alkali-soluble high-molecularcompound, a thermal negative photosensitive composition containing aphotothermal material and a thermosetting compound, a conventionalnegative photosensitive composition containing a diazo resin and analkali-soluble high-molecular compound, a conventional positivephotosensitive composition containing an o-quinine di-azide compound andan alkali-soluble high-molecular compound, and a photosensitivecomposition that can be developed in a printer.

The photosensitive layer of the thermal positive photosensitivecomposition contains the alkali-soluble high-molecular compound such asa novolak resin and the photothermal material such as a cyanine dye, andpreferably further contains an anti-soluble agent. The photosensitivelayer is not limited to a single layer, but may have a two-layeredstructure.

The photosensitive layer of the thermal negative photosensitivecomposition contains the photothermal material and the thermosettingcompound and serves to cure the region irradiated with an infrared rayto form an image area. This photosensitive layer may be a polymerizationphotosensitive layer containing an infrared absorber such as a cyaninedye, a radical generator such as an onium salt, a radical polymerizedcompound, and a binder polymer, or may be an acid cross-linkphotosensitive layer containing an infrared absorber, a thermal acidgenerator, an acid crosslinking agent, and an alkali-solublehigh-molecular compound.

The photopolymerization photosensitive composition contains a compoundhaving an ethylenically unsaturated bond, a photo-polymerizationinitiator, and an alkali-soluble high-molecular binder. Thephoto-polymerization initiator can be appropriately selected dependingon the wavelength of a light source to be used. It is preferable to forman oxygen-blocking protective layer such as polyvinyl alcohol on thephotosensitive layer.

The photosensitive layer of the photosensitive composition that can bedeveloped in a printer may be a thermo-sensitive thermoplastic fineparticle polymer or micro capsule.

A mechanism for forming an image in the image recording layer is notlimited, and an area to which energy is applied by exposure or heatingis improved in solubility or is cured, whereby the solubility todeveloper is altered.

Examples of the light source of activating rays used in exposing animage include a mercury lamp, a metal halide lamp, and a xenon lamp, andexamples of the light source for scanning exposure include a helium neonlaser, an argon laser, a KrF excimer laser, a semiconductor laser, and aYAG laser.

In the developing process, the non-cured area or the solved area in theimage recording layer is removed, thereby obtaining planographicprinting plate.

The obtained planographic printing plate is attached to a printer, andink and dampening water are supplied thereto, whereby a printing iscarried out.

The present invention is characterized by the mixture ratiodetermination process in which various recycled aluminum materialstogether with the above-mentioned support is melted by the use of amelting furnace other than the pre-rolling melting furnace to obtain arecycled bare metal with a predetermined shape and weight, and themixture ratio of the recycled bare metal, new bare metal, andtrace-metal master alloy to be introduced into the pre-rolling meltingfurnace is determined on the basis of the analysis result of theobtained recycled bare metal (or recycled melt).

FIG. 1 is a diagram illustrating a closed-loop recycling flow in themethod of recycling a planographic printing plate according to theinvention, in which a planographic printing plate having aphotosensitive image recording layer is exemplified.

The method of producing an aluminum substrate for a planographicprinting plate according to the invention is included as a part of theclosed-loop recycling flow.

Preparation of Recycled Material

In this process, recycled material is prepared. In general, anunnecessary used planographic printing plate having been subjected to aprinting is recovered and used as the recycled material.

The used planographic printing plate may be used as the recycledmaterial without any change, or may be subjected to a process ofremoving printing ink attached to the surface thereof.

As shown in FIG. 1, a used planographic printing plate 36 used forprinting in a printing company 32 is recovered by the printing company,and then sent to and processed by a recycling plant 34.

In the invention, end materials such as cut pieces of a planographicprinting plate produced in the course of producing the planographicprinting plate may be included as the recycled material in addition tothe used planographic printing plate (the end material 33 generated inprocessing a strip-shaped plate precursor shown in FIG. 1). When aprotective sheet or a packing paper is attached to the recycledmaterial, the protective sheet or the packing paper is preferablyremoved. The attached material such as image recording layer or the inkis preferably removed in advance from the recycled material beforemelting the recycled material. It is more preferable that the attachedmaterial such as the image recording layer or the ink is removed to be1% by mass or less.

The recycled material may be cut into pieces, for example, using themethod described JP-A-2000-12718 so as to improve its meltingefficiency.

Production of Recycled Bare Metal

FIG. 2 shows an example of a recycled ingot producing apparatus 38, inwhich a recycled material 40 containing the used planographic printingplate 36 generated in the printing company 32 and the end material 33with a side of 1 cm to 60 cm generated in the production plant 18 of aplanographic printing plate are processed to produce a recycled melt,and a recycled bare metal is produced.

The recycled ingot producing apparatus 38 includes a melting furnace 42melting the recycled material 40 to produce a melt 44, a casting moldsolidifying the melt 44 to form a recycled ingot 74, and a receiverreceiving the recycled ingot 74 from the lower side.

The top of the melting furnace 42 is covered with a ceiling wall 46, apartition wall vertically extends to a bottom wall from the ceiling wall46, and an introduction port 48 is disposed in a side wall. A burner 50is disposed in the other side wall opposed to the introduction port 48and serves to heat and melt the recycled material 40 introduced from theintroduction port. In the second embodiment of the invention, when therecycled material 40 starts to be partially melted by the heating fromthe outside, the recycled material partially changed to a liquid phaserapidly reaches a deep part of the anodized oxide film throughrelatively large pores formed in the anodized oxide film, whereby thehigh-temperature melt diffuses and infiltrates and the recycled materialis rapidly melted into a liquid phase.

When the melting furnace 42 is a dedicated melting furnace exclusivelymelting the recycled material 40, the variation in component purity(aluminum purity or trace metal content) of the obtained recycled melt44 can be suppressed as much as possible. In view of improvement inpurity of the recycled bare metal, it is preferable that the meltingfurnace 42 performs melting pure aluminum with an aluminum content of99.5% or more and the inside is washed before melting the recycledmaterial 40. It is also preferable that the melting furnace 42 is filledin advance with a melt up to about ⅓ to ½ the furnace capacity beforeintroducing the recycled material 40 thereto. Therefore, in the firststage of recycling, a melt of pure aluminum exists in advance by theabove-mentioned amount.

In the melting step according to the invention, it is possible toenhance the melting speed and to shorten the tact time until obtainingthe recycled melt 44, by melting the recycled material in the meltingfurnace 42 at a temperature range of from 680° C. to 900° C.

In general, in the recycled melt producing apparatus, since the recycledmaterial 40 and the melt 44 come in direct contact with air, aluminumoxide is inevitably produced at the time of heating and melting aluminummetal. Since the melted aluminum oxide is lighter than pure aluminum,the melted aluminum oxide exists in the vicinity of the surface of themelt.

In the first embodiment of the invention, since the surface of thealuminum substrate for the planographic printing plate used as therecycled material is treated by polyvinyl phosphonic acid, theproduction of aluminum oxide is reduced at the time of heating andmelting the aluminum substrate in the recycled melt producing apparatus.

In the second embodiment of the invention, since the anodized oxide filmon the surface of the aluminum substrate for the planographic printingplate used as the recycled material has pores with relatively largediameters, the aluminum substrate is efficiently liquefied for a shorttime as described above. Accordingly, since the duration of time thatthe solid state brings into contact with air (oxygen) under ahigh-temperature environment is shortened, the amount of non-desiredaluminum oxide produced by the contact of the recycled material with airunder the high-temperature environment is reduced.

When a predetermined amount of recycled material is introduced into andmelted in the melting furnace 42, it is preferable that a small amountof melt is extracted from the melt 44 for analysis in this stage.

The melt 44 from which a small amount of melt for analysis has beenextracted is supplied to a casting mold 54 having a trapezoid shapethrough a pipe 52. In this case, the total amount of melt 44 is notsupplied, but it is preferable that ⅓ to ½ of the total amount of meltis left in the melting furnace 42 so as to use the remaining melt as apreliminary melt of the next melt treatment.

The melt in the casting mold 54 is cooled by water or air and is shapedinto recycled bare metal (ingot) 74 of a trapezoid shape with 10 Kg to1200 Kg. A possible shape of the recycled ingot is shown in FIGS. 3A and3B. FIG. 3A is a plan view illustrating an example of the trapezoidshape of the recycled bare metal and FIG. 3B is a side view thereof

Analysis

In the aluminum recycling plant 34, the components of the extractedrecycled melt is analyzed. In some cases, an analysis sample may beextracted from the recycled bare metal 74. In the first embodiment ofthe invention, the aluminum purity and the content of the trace metal(such as Si, Fe, Cu, or Mn) is analyzed and Mg, Zn, Ti, and Cr can bepreferably analyzed. In the second embodiment of the invention, thealuminum purity and the content of the trace metal (such as Cu, Si, Fe,or Mn) is analyzed and Mg, Zn, Ti, and Cr can be preferably analyzed.The analysis data is also sent when the recycled bare metal is deliveredto the aluminum rolling plant 14. When the analysis is performed usingthe recycled bare metal 74, the analysis step may be performed in thealuminum rolling plant 14.

Determination of Mixture Ratio

The recycled bare metal 74 produced in the production plant 34 iscarried to the aluminum rolling plant 14, and is recycled therein. Inthe aluminum rolling plant 14, the values of the aluminum purity and thetrace metal content obtained as the result in the above-mentionedanalysis process are compared with a desired aluminum purity and adesired trace metal content of an aluminum substrate for a desiredplanographic printing plate in order to calculate differencestherebetween, and the mixture ratio of a new bare metal with adetermined aluminum purity and a trace-metal master alloy (aluminumalloy) with a determined trace-metal content with respect to therecycled bare metal is determined on the basis of the calculateddifference. By this process, the maximum mixture ratio of the recycledbare metal for accomplishing desired aluminum purity and a desired tracemetal content in the desired aluminum substrate for a planographicprinting plate can be known, and the best recycling efficiency dependingon the composition of the recycled bare metal can be achieved.

Production of Pre-rolling Melt

The recycled bare metal, the new aluminum bare metal, and thetrace-metal master alloy are introduced into the pre-rolling meltingfurnace with the mixture ratio determined in the mixture ratiodetermination process, and are heated and melted, thereby obtaining analuminum melt used for producing a support. The pre-rolling meltingfurnace is generally much greater in capacity than the recycling meltingfurnace 42 and has a scale of 100 t.

The aluminum purity of the pre-rolling melt obtained in this process ispreferably 99.0% or higher and more preferably 99.5% or higher. Thealuminum plate with aluminum purity of 99.5% or higher can be preferablyused for the electrolytic roughening treatment as described later. Whenthe aluminum purity is less than 99.0%, a problem with cracks or thelike can be easily caused at the time of rolling an aluminum plate in arolling treatment. The trace metal content is selected depending on atarget physical property of the aluminum substrate for the planographicprinting plate. In the second embodiment of the invention, the Cucontent should be in the above-mentioned range.

The melting condition may be the same as the melt producing condition inthe recycled bare metal producing process or may be properly controlleddepending on the rolling condition of the support.

Production of Aluminum Substrate

An impurity removing treatment using flux, gas, or filter is performedon the resultant aluminum melt to remove non-metal impurities orcombustion gas of the non-metal impurities, oxides, and the like and toremove H₂ gas or Na melted in the melt. The melt is processed preferablyin two steps of a method using gas and a method using filter. Theprocessed aluminum melt is cast preferably on the basis of a DC castingmethod using a twin-roll continuous caster or a fixed casting mold. Theresultant is rolled in the above-mentioned process into a predeterminedthickness and subjected to an annealing process as needed, whereby astrip-shaped aluminum substrate is produced. In general, the producedaluminum substrate 16 is stored and carried as an aluminum coil wound ina coil shape. The resultant aluminum substrate 16 is sent to theplanographic printing plate producing plant 18 in the aluminum coilstate. The recycled aluminum substrate 16 is provided to produce aplanographic printing plate precursor.

According to the invention, it is possible to efficiently recycle andproduce an aluminum substrate for a planographic printing plate.

Production of Planographic Printing Plate Precursor

The resultant aluminum substrate for a planographic printing plate isused for producing a planographic printing plate precursor. In this way,the planographic printing plate is recycled according to the invention.

Hereinafter, a method of producing a planographic printing plateprecursor using the resultant aluminum substrate for a planographicprinting plate is described.

Production of Support

In the first embodiment of the invention, the aluminum substrate 16obtained by the above-mentioned production method is first subjected toa roughening treatment required for a planographic printing platesupport. Here, one surface or both surfaces of the aluminum substrate 16are roughened.

In the second embodiment of the invention, the aluminum substrate 16formed of the aluminum alloy containing a specific amount of Cu andobtained by the above-mentioned production method is subjected to aroughening treatment required for a planographic printing plate support.Here, one surface or both surfaces of the aluminum substrate 16 areroughened.

The roughening treatment is not particularly limited, but theelectrochemical roughening treatment can be preferably used. Theelectrochemical roughening treatment is performed by performing anetching in an acid aqueous solution of hydrochloric acid or nitric acidusing AC current as electrolysis current. The acid concentration ispreferably in the range of from 3 g/L to 150 g/L and the aluminum ionconcentration in the solution is preferably adjusted to the range offrom 2 g/L to 7 g/L. The amount of electricity to be applied ispreferably in the range of from 20 C/dm² to 500 C/dm². It is preferableto use rectangular-wave current or trapezoid-wave current as the ACcurrent, and it is more preferable to use the trapezoid-wave current.

In the electrochemical roughening treatment using the electrolysismethod, the aluminum purity or the trace metal content of the aluminumsubstrate 16 has an influence on the uniformity of a produced pit,thereby affecting printing durability, contamination resistance, andexposure stability. Accordingly, the aluminum purity of the aluminumsubstrate is preferably 99.9% or higher, and more preferably 99.5% orhigher. Among the trace metals contained in the aluminum substrate 16,the Cu content is preferably in the range of 0.001% by mass to 0.050% bymass, more preferably in the range of from 0.002% by mass to 0.040% bymass, and still more preferably in the range of from 0.008% by mass to0.035% by mass. It is preferable that the Si content is in the range offrom 0.05% by mass to 0.50% by mass, the Fe content is in the range offrom 0.15% by mass to 0.7% by mass, the Mn content is in the range offrom 0.002% by mass to 0.15% by mass, the Mg content is in the range offrom 0.001% by mass to 1.5% by mass, the Zn content is in the range offrom 0.001% by mass to 0.25% by mass, the Ti content is in the range offrom 0.001% by mass to 0.10% by mass, the Cr content is in the range offrom 0.001% by mass to 0.10% by mass.

Since smut or inter-metal compound exists in the surface of the aluminumsubstrate 16 having been subjected to the roughening treatment using theabove-mentioned electrolysis method, the surface is preferably processedwith alkali and is then subjected to a cleaning treatment using an acidsolution containing sulfuric acid as a major component.

In the first embodiment of the invention, the anodization treatment isperformed on the roughened aluminum substrate 16 to form an anodizedoxide film. In the anodization treatment, an aqueous solution ofsulfuric acid, phosphoric acid, oxalic acid, or boric acid/sodium borateis used as a major component of the electrolytic solution singly or incombination. The conditions for forming the anodized oxide film is asdescribed above. The thickness of the anodized oxide film is preferablyin the range of from 0.5 μm to 1.5 μm and can be properly selected fromthis range.

Various conditions of the hydrophilizing treatment to be performedthereafter can be selected as needed. When the obtained planographicprinting plate precursor is used and then recycled again, it ispreferable in view of recycling efficiency that the hydrophilizingtreatment is performed using the polyvinyl phosphonic acid.

The hydrophilizing treatment is not limited to this method, but a knownhydrophilizing treatment such as a hydrophilizing treatment using asodium silicate solution may be properly performed. In this way, theplanographic printing plate support 16A of which the surface has beensubjected to the hydrophilizing treatment is obtained.

In the second embodiment of the invention, the anodization treatment isperformed on the roughened aluminum substrate 16 to form an anodizedoxide film. The anodization treatment can be performed as describedabove, and an aqueous solution of sulfuric acid, phosphoric acid, oxalicacid, or boric acid/sodium borate is used as the major component of theelectrolytic solution singly or in combination. It is preferable in viewof recycling efficiency of the aluminum substrate that the electrolyticsolution containing phosphoric acid as a major component is used asdescribed above. The conditions for forming the anodized oxide film isas described above. The thickness of the anodized oxide film ispreferably in the range of from 0.5 μm to 1.5 μm and can be properlyselected from this range.

Various conditions of the hydrophilizing treatment to be performedthereafter can be selected as needed.

A known hydrophilizing treatment such as a hydrophilizing treatmentusing a sodium silicate solution or a hydrophilizing treatment using apolyvinyl phosphonic acid solution may be properly performed. In thisway, the planographic printing plate support 16A of which the surfacehas been subjected to the hydrophilizing treatment is obtained.

Formation of Image Recording Layer

Then, an image recording layer is formed on the obtained support,whereby the planographic printing plate precursor is produced. In theimage recording layer forming process, a coating solution for the imagerecording layer formed of a photosensitive composition is applied to theroughened surface of the support 16A and the image recording layer isdried in the drying process.

Examples of the photosensitive compositions suitably used to form theimage recording layer according to the invention include a thermalpositive photosensitive composition containing a photothermal materialand an alkali-soluble high-molecular compound, a thermal negativephotosensitive composition containing a photothermal material and athermosetting compound, a photopolymerization photosensitivecomposition, a negative photosensitive composition containing a diazoresin and a photo-crosslink resin, a positive resin photosensitivecomposition containing a quinine di-azide compound, and a photosensitivecomposition that does not require a specific developing step.

In this manner, a strip-shaped plate precursor of a planographicprinting plate is produced, and the strip-shaped plate precursor is cutinto rectangular sheets with a predetermined size in a state in which alaminated paper is superposed on the strip-shaped plate precursor,thereby producing a planographic printing plate precursor 30 having alaminated paper attached thereto (see FIG. 1).

Plural produced planographic printing plate precursors 30 each having alaminated paper attached thereto are stacked, packed, and sent to theprinting company 32. Since the laminated paper is placed between theplanographic printing plate precursors 30 at the time of stacking theplanographic printing plate precursors 30, damages on the imagerecording layer of the planographic printing plate precursors 30 at thetime of carrying and storing the plates are effectively suppressed. Thelaminated paper is removed before forming an image on the imagerecording layer.

The planographic printing plate precursor is made up through a writingprocess (image forming step) by exposure or heating and optionallyperforming the development, thereby obtaining a planographic printingplate.

The obtained planographic printing plate is supplied with print ink anddampening water, and is then printed to a printing process.

In the method of recycling a planographic printing plate according tothe invention, a “new bare metal 100% route” 90 sending the aluminumsubstrate 16 of 100% new bare metal from the aluminum rolling plant 14to the planographic printing plate producing plant 18 is carried outonly at the first time, a “recycling route” 92 sending an aluminumsubstrate 88 containing a recycled material, which is obtained by themethod of producing an aluminum substrate for a planographic printingplate according to the invention, from the aluminum rolling plant 14 tothe planographic printing plate producing plant 18 is carried out at thesecond time or later.

In the method according to the invention, it is possible to construct acomplete closed-loop recycling flow for recycling aluminum scrapsgenerated in the field of planographic printing plate industry. As aresult, it is possible to greatly reduce the generation of CO₂, comparedwith the case in which an aluminum substrate for a planographic printingplate is produced using only the new aluminum bare metal 12 produced byan aluminum refining plant 10.

Therefore, in the method according to the invention, it is possible toguarantee the quality of the aluminum purity and the trace metal contentin the obtained aluminum substrate for a planographic printing plate, toimprove the energy loss and the yield loss markedly, and to greatlyreduce the generation of CO₂ in production of the planographic printingplate precursor.

EXAMPLES

Hereinafter, examples of the invention is described, but the inventionis not limited to the examples.

Examples 1-1 and 1-2 and Comparative Example 1-1

1. Production of Aluminum Substrate

A melt was produced using aluminum alloy containing 0.073% by mass ofSi, 0.270% by mass of Fe, 0.028% by mass of Cu, 0.001% by mass of Mn,0.001% by mass of Cr, 0.003% by mass of Zn, 0.020% by mass of Ti and thebalance of Al and inevitable impurities, and an aluminum substrate usedin Example 1-1 was produced as follows.

First, a melt process including degassing and filtering was performed tothe aluminum alloy melt and a cast ingot with a thickness of 500 mm wasproduced using a DC casting method. The surface of the obtained castingot was face-milled by 10 mm, the cast ingot was heated, the hotrolling was started at 400° C. without soaking the cast ingot, and thenthe resultant was rolled up to the thickness of 4 mm. Then, theresultant was cold-rolled up to the thickness of 1.5 mm, processannealing was carried out thereon, the resultant was cold-rolled up to0.24 mm, and the flatness was corrected, thereby obtaining an aluminumplate (aluminum substrate).

2. Production of Planographic Printing Plate Support (Surface Treatmentof Aluminum Substrate)

The obtained aluminum plate was subjected to the surface treatment inthe following process. After the surface treatment and the waterwashing, liquid-cutting was carried out with a nip roller. The waterwashing was carried out by ejecting water from a spray tube.

2-1. Mechanical Roughening Treatment

First, a mechanical roughening treatment was carried out using a brushroller with a rotating nylon brush formed of 6,10-nylon and having ahair length of 50 mm, and a hair diameter of 0.48 mm while supplying asuspension of silica (abrading agent, average particle diameter of 25μm) with a specific gravity of 1.12 and water as a grinding slurry tothe surface of the aluminum plate.

2-2. Chemical Roughening Treatment

Subsequently, an aqueous solution with a temperature of 70° C.containing 27% by mass of NaOH and 6.5% by mass of aluminum ions wasejected to the aluminum plate to perform an alkali etching process. Theamount of melted aluminum plate was 8 g/m². An aqueous solution ofnitric acid with a temperature of 35° C. was sprayed to the aluminumplate to perform a desmutting treatment for 10 seconds.

2-3. Electrochemical Roughening Treatment

An electrochemical roughening treatment was carried out usingtrapezoid-wave AC current and using an aqueous solution of nitric acidcontaining 1% by mass of nitric acid (which contains 0.5% by mass ofaluminum ions and 0.007% by mass of ammonium ions at a temperature of50° C.). The current density at the peak of the AC current was 50 A/dm²when the aluminum plate was used as an anode and a cathode, the ratio ofthe amount of electricity of the AC current as the cathode to the amountof electricity as the anode was 0.95, the duty ratio was 0.50, thefrequency was 60 Hz, and the total amount of electricity as the anodewas 180 C/dm².

Thereafter, the water washing was carried out. Subsequently, an aqueoussolution with a temperature of 45° C. containing 26% by mass of NaOH and6.5% by mass of aluminum ions was ejected to the aluminum plate by aspray to perform an alkali etching process. The amount of meltedaluminum plate was 3 g/m². Then, a sulfuric acid solution (with asulfuric acid concentration of 300 g/L and an aluminum ion concentrationof 15 g/L) was ejected to the aluminum plate from a spray tube at 80° C.for 7 seconds to perform an acid etching process. Thereafter, the waterwashing was carried out.

2-4. Anodization Treatment

Subsequently, an anodization treatment was carried out on the aluminumplate under the conditions of a current density of 25 A/dm², atemperature of 50° C., and a time of 30 seconds, by using an aqueoussolution with a sulfuric acid concentration of 100 g/L (containing 0.5%by mass of aluminum ions) as an anodizing solution and using a DCvoltage, whereby an oxide film with a thickness of 1.5 μm was formed.Thereafter, the water washing was carried out by the use of a spray.

2-5. Hydrophilizing Treatment Using Aqueous Solution of PolyvinylPhosphonic Acid

The resultant aluminum substrate was immersed in an aqueous solution of0.6% polyvinyl phosphonic acid (an aqueous solution produced using wellwater) at a solution temperature of 60° C. for 30 seconds. In this way,an aluminum substrate (1) of a planographic printing plate was obtained.The amount of attached material measured using a fluorescent X ray was18.8 mg/m² in terms of an amount of phosphorous element.

3. Production of Planographic Printing Plate Precursor (Formation ofImage Recording Layer) 3-1. Undercoating

A 3% methanol solution of copolymer of p-vinyl benzoate acid andvinylbenzyl triethylammonium chloride (copolymerization mole ratio of85/15, Mw 28,000) was applied to the processed surface of the support bythe use of a bar coater to form an undercoating layer so that thecoating amount after drying is 18 mg/m².

3-2. Formation of Recording Layer (Intermediate Layer)

The following lower layer coating solution was applied to the aluminumsubstrate having the undercoating layer formed thereon by the use of thebar coater so that the coating amount after drying is 0.85 g/m², and wasthen dried at 160° C. for 44 seconds, thereby forming a lower layer.Thereafter, the following upper layer coating solution was appliedthereto by the use of the bar coater so that the coating amount afterdrying is 0.22 g/m², and was then dried at 148° C. for 25 seconds,thereby forming a planographic printing plate precursor.

Lower Layer Coating Solution

N-(4-aminosulfonylphenyl) methacrylamide/acrylonitrile/methylmethacrylate (36/34/30: Mw 60,000)  1.73 g m,p-cresol novolak (m/p ratio= 6/4, Mw 4,500)  0.192 g Cyanine dye A (below structure)  0.134 g3-methoxy-4-diazodiphenyl amine hexafluorophosphate  0.032 g Ethylviolet   0.0781 g Polymer 1 (below structure)  0.035 g Methyl ethylketone 25.41 g 1-methoxy-2-propanol 12.97 g γ-butyrolactone 13.18 gCyanine dye A

Polymer 1

Upper Layer Coating Solution

m,p-cresol novolak (m/p ratio = 6/4, Mw 4,500)   0.3479 g Cyanine dye A(above structure)   0.0192 g Polymer 1 (above structure)  0.015 gQuaternary ammonium salt (below structure)   0.0043 g Methyl ethylketone  6.79 g 1-methoxy-2-propanol 13.07 g Quaternary ammonium salt

3-3. Production of Planographic Printing Plate and Printing

A test pattern was formed as an image on the planographic printing plateprecursor with TRENDSETTER (trade name, manufactured by Creo).

Thereafter, a developing process was carried out at a developingtemperature of 30° C. for a developing time of 12 seconds by the use ofPS processor LP940H (trade name, manufactured by Fujifilm Corporation)and provided with developer DT-2 (trade name, manufactured by FujifilmCorporation). After the development, the resultant plate was provided tocontinuous printing using printer RISURON (trade name, manufactured byKomori Corporation).

4. Preparation of Recycled Material

The print ink attached to the surface of the planographic printing platehaving been subjected to the printing was removed with a petroleumcleanser and the plate was detached from the printer. The usedplanographic printing plate was cut into small pieces with the greatestlength of 5 mm to 50 mm using an electrical cutter. Foreign substancesare separated from the raw material cut into small pieces using asuction separation method and then using a magnetic separation method.The recycled material obtained from the planographic printing platesupport is called recycled material (1).

5. Production of Recycled Bare Metal

In the recycling plant, first, 1.5 t of aluminum melt with a purity of100% was melted in the melting furnace 42 of the recycled ingotproducing apparatus 38 shown in FIG. 2. 1.5 t of the recycled material(1) was introduced thereto and was heated and melted at 720° C., therebyobtaining melt (1). Then, analysis samples were extracted from the melt.

Thereafter, the melt was made to flow into the casting mold 54 through apipe 52, and was cooled and solidified so as to have the size shown inFIGS. 3A and 3B, whereby recycled bare metal (ingot) was obtained.

Aluminum oxide slab floated over the melt surface was removed, the massthereof was measured, and the corresponding weight of aluminum wassubtracted from an ideal amount of aluminum when it is assumed that nooxidation is occurred, whereby the recycled bare metal yield wascalculated.

The aluminum purity and the trace metal content of the analysis samplewere analyzed. As a result, the melt (1) contained Si of 0.070%, Fe of0.300%, Cu of 0.015%, and Mg of 0.010%.

The analysis result was sent to the aluminum rolling plant 14 along withthe bare metal.

6. Production of Aluminum Substrate for Planographic Printing Plate

In the aluminum rolling plant, an aluminum substrate for a planographicprinting plate is produced in accordance with the order given from theplanographic printing plate producing plant, and the order includes thealloy composition in addition to the thickness, size, and amount of thealuminum substrate.

Therefore, when the aluminum rolling plant 14 produces the aluminumsubstrate for a planographic printing plate using the delivered recycledbare metal, the alloy composition included in the order is sets as atarget, the alloy composition is compared with the analysis values sentalong with the recycled bare metal to calculate the differencestherebetween, and the amounts of recycled bare metal, trace-metal masteralloy, and pure aluminum to be mixed with the target value of the alloycomposition and a predetermined amount of aluminum melt in thepre-rolling melting furnace are arithmetically calculated. By this step,the maximum mixture ratio of the recycled bare metal can be known,thereby obtaining the best recycling efficiency depending on thecomposition of the recycled bare metal.

For example, when the target values are Si of 0.07%, Fe of 0.25%, Cu of0.025%, and Mg equal to or less than 0.01%, the capacity of thepre-rolling melting furnace is 100 t and when the recycled bare metalwith the composition of the present embodiment is used, it is possibleto obtain the target alloy composition by mixing 83 t of the recycledbare metal and 17 t of the pure aluminum bare metal and adjusting thecontents of Si and Cu by the addition of master alloys.

Therefore, the recycled bare metal, the new aluminum bare metal, and thetrace-metal master alloy were introduced into the pre-rolling meltingfurnace in accordance with the mixture ratio determined in the mixtureratio determination process, and the resultant was heated and melted,thereby obtaining a pre-rolling aluminum melt.

The degassing process and the filtering treatment were performed on thealuminum melt to remove impurities, and then an aluminum substrate wasproduced using the same DC casting method as described in “1. Productionof Aluminum substrate” above.

A planographic printing plate support was produced similarly to “2.Production of planographic printing plate support” above, except thatthe above-obtained aluminum substrate is used as a raw material in placeof using the new aluminum.

When 50 t of a new planographic printing plate was produced using theused planographic printing plate (PS plate) obtained by the method ofproducing an aluminum substrate for a planographic printing plate as araw material and when 50 t of a planographic printing plate (PS plate)was produced using 100% of the raw material (new bare metal) of thealuminum substrate used in Example 1 (Control 1-1), the amounts of CO₂generated were measured in the aluminum refining process, the recycledbare metal producing process, the aluminum substrate producing process,and the planographic printing plate producing process, and themeasurement results were shown in Table 1. The recycled bare metal yieldwas also shown in Table 1.

Example 1-2

A planographic printing plate precursor of Example 1-2 was producedsimilarly to Example 1-1, except that the polyvinyl phosphonate solutiontreatment in the step of 2-5 of Example 1-1 is replaced with theimmersion treatment in 0.5% of polyvinyl phosphonate solution at asolution temperature 40° C. for 30 seconds. The amount of phosphorouselement measured using a fluorescent X ray was 9.8 mg/m². Theplanographic printing plate precursor was used in printing, and was thenrecycled in the same way to produce a new planographic printing plateprecursor, which was evaluated in the same way as Example 1-1.

Comparative Example 1-1

A planographic printing plate precursor of Comparative Example 1-1 wasproduced similarly to Example 1-1, except that the polyvinyl phosphonatesolution treatment is not performed. The produced planographic printingplate was used in printing, and was then recycled in the same way toproduce a new planographic printing plate precursor, which was evaluatedin the same way as Example 1-1. The evaluation result is also shown inTable 1.

TABLE 1 Example Example Comparative Control 1-1 1-2 Example 1-1 1-1Yield of recycled bare 95.2 94.8 93 — metal (%) Amount of carbon 1.5 1.51.51 10.41 dioxide generated in producing aluminum substrate (t/1t)

The amount of CO₂ generated in the recycled bare metal producing processwas calculated from the energy and the yield at the time of melting therecycled material. Data appearing on the website of the Japan AluminumAssociation was used as the amounts of CO₂ generated in the aluminumrefining process and the rolling process.

As can be seen from Table 1, in Example 1-1 and Example 1-2 in which theplanographic printing plate was produced using the production methodaccording to the invention, the amount of CO₂ can be reduced up to about¼ of the amount of CO₂ generated in the case (Control 1-1) in which newbare metal was used at an amount of 100% (that is, a 75% reduction canbe achieved). On the other hand, in Comparative Example 1-1 using thesupport not subjected to the polyvinyl phosphonate treatment, thealuminum purity obtained after the recycled bare metal producing processwas lower than that in Examples 1-1 and 1-2.

As can be seen from Table 1, in Example 1-1 and Example 1-2 in which theplanographic printing plate was produced using the production methodaccording to the invention, the amount of CO₂ can be reduced up to about15% of the amount of CO₂ generated in the case (Control 1-1) in whichnew bare metal was used at an mount of 100% (that is, a 85% reductioncan be achieved). On the other hand, in Comparative Example 1-1 usingthe support not subjected to the polyvinyl phosphonate process, theyield of the recycled bare metal was lower than that in Examples 1-1 and1-2.

Examples 2-1 and 2-2 and Comparative Example 2-1

1. Production of Aluminum Substrate

A melt was produced using aluminum alloy containing 0.073% by mass ofSi, 0.270% by mass of Fe, 0.028% by mass of Cu, 0.001% by mass of Mn,0.001% by mass of Cr, 0.003% by mass of Zn, 0.020% by mass of Ti and thebalance of Al and inevitable impurities, and an aluminum substrate usedin Example 2-1 was produced as follows.

First, a melt process including degassing and filtering was performed tothe aluminum alloy melt and a cast ingot with a thickness of 500 mm wasproduced using a DC casting method. The surface of the obtained castingot was face-milled by 10 mm, the cast ingot was heated, the hotrolling was started at 400° C. without soaking the cast ingot, and thenthe resultant was rolled up to the thickness of 4 mm. Then, theresultant was cold-rolled up to the thickness of 1.5 mm, processannealing was carried out thereon, the resultant was cold-rolled up to0.24 mm, and the flatness was corrected, thereby obtaining an aluminumplate (aluminum substrate).

2. Production of Planographic Printing Plate Support (Surface Treatmentof Aluminum Substrate)

The obtained aluminum plate was subjected to the surface treatment inthe following process. After the surface treatment and the waterwashing, liquid-cutting was carried out with a nip roller. The waterwashing was carried out by ejecting water from a spray tube.

2-1. Electrochemical Roughening Treatment

An electrochemical roughening treatment was performed on the obtainedaluminum plate in a hydrochloric acid bath of a hydrochloric acidsolution (17 g/L) using trapezoid-wave AC current. The current densityat the peak of the AC current was 50 A/dm² when the aluminum plate wasused as an anode and a cathode, the ratio of the amount of electricityof the AC current as the cathode to the amount of electricity as theanode was 0.95, the duty ratio was 0.50, the frequency was 60 Hz, andthe total amount of electricity as the anode was 180 C/dm².

Thereafter, the water washing was carried out. The maximum surfaceroughness of the aluminum plate was 4 μm.

2-2. Anodization Treatment

Subsequently, an anodization treatment was carried out on the aluminumplate under the conditions of a current density of 4 A/dm², atemperature of 40° C., and a time of 30 seconds, by using an aqueoussolution with a phosphoric acid concentration of 40% by mass (containing0.5% by mass of aluminum ions) as an anodizing solution and using a DCvoltage, whereby an oxide film was formed. Thereafter, the water washingwas carried out by the use of a spray. The formed anodized oxide filmwas analyzed with an electron microscope. As a result, pores with anaverage pore diameter of 750 A were found by 175/m².

2-3. Hydrophilizing Treatment

The resultant aluminum substrate was immersed in an aqueous solution of0.6% polyvinyl phosphonic acid (an aqueous solution produced using wellwater) at a solution temperature of 60° C. for 30 seconds. In this way,an aluminum substrate (2) of a planographic printing plate was obtained.The amount of attached material measured using a fluorescent X ray was18.8 mg/m² in terms of an amount of phosphorous element.

Similarly to “3. Production of planographic printing plate precursor(Formation of image recording layer)”, a planographic printing plateprecursor was produced using the obtained support.

Similarly to “4. Preparation of recycled material”, the recycledmaterial was obtained using the planographic printing plate used inprinting.

Similarly to “5. Production of recycled bare metal”, the recycledmaterial was obtained and the yield of the recycled bare metal wascalculated using the obtained recycled material.

The aluminum purity and the trace metal content of the analysis samplewere analyzed. As a result, the obtained melt (2) contained Si of0.070%, Fe of 0.300%, Cu of 0.015%, and Mg of 0.010%.

The analysis result was sent to the aluminum rolling plant 14 along withthe recycled bare metal.

Similarly to “6. Production of aluminum substrate for planographicprinting plate”, the aluminum substrate was cast.

A planographic printing plate support was produced similarly to “2.Production of planographic printing plate support” using theabove-obtained aluminum substrate as a raw material and using newaluminum.

When 50 t of a new planographic printing plate was produced using theused planographic printing plate (PS plate) obtained by the method ofproducing an aluminum substrate for a planographic printing plate as araw material and when 50 t of a planographic printing plate (PS plate)was produced using 100% of the raw material (new bare metal) of thealuminum substrate used in Example 2-1 (Control 2-1), the amounts of CO₂generated were measured in the aluminum refining process, the recycledbare metal producing process, the aluminum substrate producing process,and the planographic printing plate producing process, and themeasurement results were shown in Table 2. The recycled bare metal yieldwas also shown in Table 2.

Example 2-2

A planographic printing plate precursor of Example 2-2 was producedsimilarly to Example 2-1, except that the conditions of the aluminumsubstrate anodizing process are changed as follows. The planographicprinting plate precursor was used in printing and was then recycled inthe same way to produce a new planographic printing plate precursor,which was evaluated in the same way as Example 2-1.

Condition of Anodization Treatment

An anodization treatment was carried out on the aluminum plate under theconditions of a current density of 4 A/dm², a temperature of 40° C., anda time of 30 seconds, by using an aqueous solution with a phosphoricacid concentration of 30% by mass and a sulfuric acid concentration of10% by mass (containing 0.5% by mass of aluminum ions) as an anodizingsolution and using a DC voltage, whereby an oxide film was formed.Thereafter, the water washing was carried out by the use of a spray. Theformed anodized oxide film was analyzed with an electron microscope. Asa result, pores with an average pore diameter of 500 Å were found by200/μm².

Comparative Example 2-1

A planographic printing plate precursor was produced similarly toExample 2-1, except that the conditions of the aluminum substrateanodizing process are changed as follows. The planographic printingplate precursor was used in printing and was then recycled in the sameway to produce a new planographic printing plate precursor, which wasestimated in the same way as Example 2-1.

Condition of Anodization Treatment

An anodization treatment was carried out on the aluminum plate under theconditions of a current density of 6 A/dm², a temperature of 30° C., anda time of 30 seconds, by using an aqueous solution with a sulfuric acidconcentration of 30% by mass (containing 0.5% by mass of aluminum ions)as an anodizing solution and using a DC voltage, whereby an oxide filmwas formed. Thereafter, water washing was carried out by the use of aspray. The formed anodized oxide film was analyzed with an electronmicroscope. As a result, pores with an average pore diameter of 130 Åwere found by 1000/μm² or more.

TABLE 2 Example Example Comparative Control 2-1 2-2 Example 2-1 2-1Yield of recycled bare 95.5 94.3 92.8 — metal (%) Amount of carbon 1.501.50 1.51 10.41 dioxide generated in producing aluminum substrate (t/1t)

The amount of CO₂ generated in the recycled bare metal producing processwas calculated from the energy and the yield at the time of melting therecycled material. Data appearing on the website of the Japan AluminumAssociation was used as the amounts of CO₂ generated in the aluminumrefining process and the rolling process.

As can be seen from Table 2, in Example 2-1 and Example 2-2 in which theplanographic printing plate was produced using the production methodaccording to the invention, the amount of CO₂ can be reduced up to about¼ of the amount of CO₂ generated in the case (Control 2-1) in which newbare metal was used at an amount of 100% (that is, a 75% reduction canbe achieved). On the other hand, in Comparative Example 2-1 using asupport in which the Cu content in the aluminum alloy as a raw materialof the aluminum substrate departs from the range according to theinvention, the aluminum purity obtained after the recycled bare metalproducing process was lower than that in Examples 2-1 and 2-2.

As can be seen from Table 2, in Example 2-1 and Example 2-2 in which theplanographic printing plate was produced using the production methodaccording to the invention, the amount of CO₂ can be reduced up to about15% of the amount of CO₂ generated in the case (Control 2-1) in whichnew bare metal was used at an amount of 100% (that is, a 85% reductioncan be achieved). On the other hand, in Comparative Example 2-1 using asupport formed of aluminum alloy in which the Cu content departs fromthe range according to the invention, the yield of the recycled baremetal was lower than that in Examples 2-1 and 2-2.

All publications, patent applications, and technical standards mentionedin this specification are herein incorporated by reference to the sameextent as if each individual publication, patent application, ortechnical standard was specifically and individually indicated to beincorporated by reference.

1. A method of producing an aluminum substrate for a planographicprinting plate, the method sequentially comprising: preparing a recycledmaterial including a used planographic printing plate having aplanographic printing plate support obtained by treating an aluminumsubstrate; producing a recycled bare metal by introducing the obtainedrecycled material into a melting furnace, melting the recycled materialat a temperature of from 680° C. to 900° C. to obtain a recycledmaterial melt, and shaping the recycled material melt into apredetermined shape with a predetermined weight; analyzing the aluminumpurity and a trace metal content of the obtained recycled bare metal;comparing analysis values of the aluminum purity and the trace metalcontent of the obtained recycled bare metal with a desired aluminumpurity and a desired trace metal content predetermined for aplanographic printing plate support in order to calculate differencestherebetween, and determining a mixture ratio of a new aluminum baremetal and a trace-metal master alloy with a determined purity withrespect to the recycled bare metal on the basis of the calculateddifferences; producing a pre-rolling melt by introducing the recycledbare metal, the new aluminum bare metal, and the trace-metal masteralloy into a pre-rolling melting furnace at amounts corresponding to thedetermined mixture ratio, and heating and melting; and producing astrip-shaped aluminum substrate by rolling the obtained pre-rollingmelt.
 2. The method of producing an aluminum substrate for aplanographic printing plate according to claim 1, wherein theplanographic printing plate support is obtained by sequentiallyperforming a roughening treatment, an anodization treatment, and ahydrophilizing treatment using an aqueous solution including polyvinylphosphonic acid on the aluminum substrate.
 3. The method of producing analuminum substrate for a planographic printing plate according to claim2, wherein the recycled material further includes at least one of cutpieces of the aluminum substrate or cut pieces of the planographicprinting plate, which are generated during producing the planographicprinting plate.
 4. The method of producing an aluminum substrate for aplanographic printing plate according to claim 1, wherein theplanographic printing plate support is obtained by sequentiallyperforming a roughening treatment and an anodization treatment using anelectrolytic solution including phosphoric acid on the aluminumsubstrate.
 5. The method of producing an aluminum substrate for aplanographic printing plate according to claim 4, wherein the recycledmaterial further includes at least one of cut pieces of the aluminumsubstrate or cut pieces of the planographic printing plate, which aregenerated during producing a planographic printing plate precursor. 6.The method of producing an aluminum substrate for a planographicprinting plate according to claim 4, wherein a content of the phosphoricacid in the electrolytic solution is in a range of from 10% by mass to50% by mass.
 7. A method of recycling a planographic printing plate, themethod sequentially comprising: producing a planographic printing platesupport obtained by treating an aluminum substrate for the planographicprinting plate; producing a planographic printing plate precursor byforming an image recording layer on the treated surface of theplanographic printing plate support; processing the obtainedplanographic printing plate precursor to obtain a planographic printingplate and performing a desired printing on the obtained planographicprinting plate; recovering the used planographic printing plategenerated after printing; and recycling the recovered planographicprinting plate by providing the recovered planographic printing plate asthe recycled material of an aluminum substrate in the method ofproducing an aluminum substrate for a planographic printing plate ofclaim
 1. 8. The method of recycling a planographic printing plateaccording to claim 7, wherein the planographic printing plate support isobtained by sequentially performing a roughening treatment, ananodization treatment, and a hydrophilizing treatment using an aqueoussolution including polyvinyl phosphonic acid on at least one surface ofan aluminum substrate for the planographic printing plate.
 9. The methodof recycling a planographic printing plate according to claim 8, whereinthe aluminum substrate for the planographic printing plate is thealuminum substrate for the planographic printing plate obtained by themethod of producing an aluminum substrate for a planographic printingplate according to claim
 2. 10. The method of recycling a planographicprinting plate according to claim 7, wherein the planographic printingplate support is obtained by sequentially performing a rougheningtreatment and an anodization treatment using an electrolytic solutionincluding phosphoric acid on at least one surface of an aluminumsubstrate for the planographic printing plate.
 11. The method ofrecycling a planographic printing plate according to claim 10, whereinthe aluminum substrate for the planographic printing plate is thealuminum substrate for the planographic printing plate obtained by themethod of producing an aluminum substrate for a planographic printingplate according to claim 4.